Many factors contribute to the formation of saccular aneurysms, particularly neural aneurysms. One of the major contributors is wall shear stress (WSS), which in addition to hypertension leads to a reduction in the elastic tissue of the tunica media, thereby contributing to the formation of the aneurysm. The effect of wall shear stress is heightened at certain anatomical geometries such as bifurcations.
It is known to try to treat aneurysms by filling the aneurysmal sac with filler such as a prosthetic coil. The methodology behind the use of prosthetic coils is to establish a hard thrombus formation within the sac of the aneurysm as a means of isolating the aneurysm wall from the flow of blood. While this can be effective in the treatment of many types of aneurysm, it is less effective when the aneurysm occurs at a bifurcation or trifurcation, such as at the base of the basilar artery. Furthermore, filling an aneurysm does not necessarily reduce the pressure applied to the wall of the aneurysm sac caused by the blood flow.
It is also known to close off the entrance to the aneurysmal sac or to divert the flow of fluid therefrom, but known devices do not always effectively reduce blood flow into the sac or pressure applied to its wall.
Examples of devices for treating aneurysms can be found in U.S. 2002/0179166, U.S. 2002/0198591, U.S.-2003/0100945, U.S.-2010/0106180 and WO 2012/102919.